Resolved Ages and Stellar Metallicities in Progenitors of Milky Way Analogs: A Closer Look at their Star Formation Histories since z=5
Abstract
We present the evolution of the resolved mass-weighted age, stellar metallicity, and sSFR of 872 Milky Way Analog (MWA) progenitors up to redshift z=5 from the Canadian Unbiased Cluster Survey (CANUCS). The metallicity and mass-weighted ages were obtained via spatially resolved SED-fitting with the non-parametric code Dense Basis. We split the sample into mergers versus non-mergers using the merger parameter from the Gini-M20 plane obtained through Gini-M20 analysis of the morphology of the stellar mass maps with Statmorph. Across our redshift range, non-mergers have negative or flat average age gradients from −0.022 to 0.005 dex/kpc, and positive or flat sSFR gradients from −0.089 to 0.092 dex/kpc, consistent with inside-out assembly. The average log(Z/Zsun) gradients for non-mergers range from −0.029 to 0.044 dex/kpc, however, positive gradients only appear between 2 < z < 3. At every redshift epoch, mergers typically have flatter age gradients, more negative sSFR gradients, and similar metallicity gradients compared to non-mergers. We divide the property maps of ongoing mergers into separate regions based on their component galaxies, and find little to no difference between the components' average ages or metallicities, but the less massive of the merging system is on average 0.1−0.4 dex higher in sSFR. Our results point to major mergers contributing some momentary disruption to the general trend of inside-out mass assembly, but does not upend the overall picture of MWA disks growing inside-out over cosmic time.
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BibTeX
@misc{tan2026resolved,
title = {{Resolved Ages and Stellar Metallicities in Progenitors of Milky Way Analogs: A Closer Look at their Star Formation Histories since $z=5$}},
author = {Vivian Yun Yan Tan and Adam Muzzin and Naadiyah Jagga and Visal Sok and Ghassan T. E. Sarrouh and Gregor Rihtaršič and Roberto Abraham and Yoshihisa Asada and Maruša Bradač and Kartheik Iyer and Nicholas S. Martis and Gaël Noirot and Marcin Sawicki and Chris J. Willott and Sunna Withers},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2606.21651},
eprint = {2606.21651},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.21651},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Resolved Ages and Stellar Metallicities in Progenitors of Milky Way Analogs: A Closer Look at their Star Formation Histories since z=5
AU - Vivian Yun Yan Tan
AU - Adam Muzzin
AU - Naadiyah Jagga
AU - Visal Sok
AU - Ghassan T. E. Sarrouh
AU - Gregor Rihtaršič
AU - Roberto Abraham
AU - Yoshihisa Asada
AU - Maruša Bradač
AU - Kartheik Iyer
AU - Nicholas S. Martis
AU - Gaël Noirot
AU - Marcin Sawicki
AU - Chris J. Willott
AU - Sunna Withers
PY - 2026
DA - 2026/09/29
PB - arXiv
DO - 10.48550/arxiv.2606.21651
UR - https://arxiv.org/abs/2606.21651
AB - We present the evolution of the resolved mass-weighted age, stellar metallicity, and sSFR of 872 Milky Way Analog (MWA) progenitors up to redshift z=5 from the Canadian Unbiased Cluster Survey (CANUCS). The metallicity and mass-weighted ages were obtained via spatially resolved SED-fitting with the non-parametric code Dense Basis. We split the sample into mergers versus non-mergers using the merger parameter from the Gini-M_20 plane obtained through Gini-M_20 analysis of the morphology of the stellar mass maps with Statmorph. Across our redshift range, non-mergers have negative or flat average age gradients from −0.022 to 0.005 dex/kpc, and positive or flat sSFR gradients from −0.089 to 0.092 dex/kpc, consistent with inside-out assembly. The average log(Z/Zsun) gradients for non-mergers range from −0.029 to 0.044 dex/kpc, however, positive gradients only appear between 2 < z < 3. At every redshift epoch, mergers typically have flatter age gradients, more negative sSFR gradients, and similar metallicity gradients compared to non-mergers. We divide the property maps of ongoing mergers into separate regions based on their component galaxies, and find little to no difference between the components' average ages or metallicities, but the less massive of the merging system is on average 0.1−0.4 dex higher in sSFR. Our results point to major mergers contributing some momentary disruption to the general trend of inside-out mass assembly, but does not upend the overall picture of MWA disks growing inside-out over cosmic time.
ER -